Civilization’s Future

Sustainability

June 27th, 2008

Sustainability is today’s political hot phrase. It conveys an image of eternal security. If we live sustainably then tomorrow will be all right. Given Earth’s record over its 4.5 billion year existence, eternal security is nothing more than a pipe dream. Nevertheless, let’s explore this further.

Autotrophs capture the sun’s energy. We use the autotrophs. Estimates of net primary productivity indicate that autotrophs add about 100 gigatonnes of dry matter annually. Given average energy densities, this equates to 1.87e21 Joules captured every year. This has been and continues to be the only reliable source of renewable energy.

A person needs about 4e9 Joules each year to power their body. As well, typically energy has a 10% efficiency transfer from autotrophs to heterotrophs. This allows for 46 billion people if all were vegetarian. Substantially fewer are possible if all were carnivores. But, this means no other animals on Earth, whether herbivore or carnivore, as all the autotroph’s energy is taken by people.

Now lets consider people’s other energy needs. We know that city dwellers use 350 times more energy in order to power their technology. And, today more than half of the humanity resides in cities. Given this, the Earth could sustain about half a billion people, a far cry less than the 46 billion vegetarians that are theoretically possible.

Thus, if we maximize our population, we loss our technology as well as destroy the Earth’s ecosystem. Yet, we already have more than 10 times the sustainable number of people. How does this real interpretation of sustainability become accepted?

See the BOOK

Posted in Autotrophs | No Comments »

Civilization’s Future

Sustainability

Pages

Archives

Categories

Futurists

Meta